Zadanie 19
Which of the following processes are exothermic? I. K(g) → K+(g) + e− II. H2O(g) → H2O(l) III. Ag+(g) + Cl−(g) → AgCl(s) A. I and II only B. I and III only C. II and III only D. I, II and III
Endothermic and exothermic reactions
Classify reactions as exothermic or endothermic from the direction of energy transfer, predict the temperature rise or fall observed in the surroundings during each type, and relate the sign of ΔH to each.
Tę umiejętność sprawdza 18 zadań wzorowanych na arkuszach IB z lat 2022–2026.
Zadania sprawdzające tę umiejętność: 18 Otwórz w wyszukiwarce z filtrami
Zadanie 19
The diagram shows the energy profile of a reaction. Which expression could give the enthalpy change, ΔH, of this reaction in kJ mol−1? A. +87 − 215 B. −215 + 87 C. +215 − 87 D. −215 − 87
- Materiał graficzny
Zadanie 1b
The sealed vessel was left for the reaction to proceed. Suggest two properties of the system, other than its colour, that could be measured to follow the progress of the reaction over time, and predict how each would change as the forward reaction proceeds.
Zadanie 3a
Suppose carbonyl dibromide were made by a free-radical chain reaction of carbon monoxide, CO, with bromine vapour, Br2, started by ultraviolet light. The questions below treat this hypothetical route with the bond-enthalpy model and the entropy…
- Tabela do uzupełnienia
- Materiał graficzny
Zadanie 18
The energy profile below was recorded for a reaction. Which pair of statements is consistent with it? In each option the first statement compares the enthalpy of the products with that of the reactants and the second gives the sign of ΔH. A. products…
- Materiał graficzny
Zadanie 20
Which row correctly describes an endothermic reaction? A. The temperature of the surroundings rises and the products are more stable than the reactants. B. The temperature of the surroundings falls and the products are more stable than the reactants. C. The…
Zadanie 23
A student stirred 0.030 mol of solid sodium hydrogencarbonate into 40 cm3 of a 1.0 mol dm−3 solution of ethanedioic acid. H2C2O4(aq) + 2 NaHCO3(s) → Na2C2O4(aq) + 2 CO2(g) + 2 H2O(l) The temperature of the solution fell from…
Zadanie 3b
The forward reaction is endothermic, uses platinum as a catalyst, and takes place at 800 K. Sketch the reaction's energy profile both with and without the catalyst present, labelling the activation energies and ΔH.
- Materiał graficzny
Zadanie 20
The potential energy profile of a reaction is shown. Which reaction has this energy profile? A. Cl2(g) → 2 Cl(g) B. CaCO3(s) → CaO(s) + CO2(g) C. N2O4(g) → 2 NO2(g) D. 2 Mg(s) + O2(g) → 2 MgO(s)
- Materiał graficzny
Zadanie 20
A student mixes a solution of citric acid with solid sodium hydrogencarbonate in an insulated polystyrene cup fitted with a thermometer. The energy profile of the reaction is shown. Which combination is correct? A. the temperature of the solution rises;…
- Materiał graficzny
Zadanie 5c
Propenal can be made by the dehydration of propane-1,2,3-triol (glycerol). CH2(OH)CH(OH)CH2OH(l) → CH2=CHCHO(g) + 2 H2O(g) (i) Calculate the standard enthalpy change of this reaction, using ΔHf⊖ of propenal(g)…
Zadanie 1a
Outline why the first ionization energies of all the elements in the table are positive, whereas the first electron affinities of most of them are negative.
- Materiał graficzny
Zadanie 2f
The conversion of carbon dioxide to methanol is usually carried out over a catalyst containing copper and zinc oxide. (i) Sketch energy profiles for the forward reaction, with and without the catalyst, on the axes shown. Label ΔH and the two activation…
- Materiał graficzny
Zadanie 14
Which changes are exothermic? I. CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(l) II. Cl(g) + e− → Cl−(g) III. H2O(l) → H2O(g) A. I and II only B. I and III only C. II and III only D. I, II and III
Zadanie 14
Which of these changes are exothermic? I. N2(g) + 3 H2(g) → 2 NH3(g) II. I2(s) → I2(g) III. H2O(g) → H2O(l) A. I and II only B. I and III only C. II and III only D. I, II and III
Zadanie 16
Which expression gives the enthalpy change, ΔH, of the forward reaction shown in the enthalpy profile? A. II − I B. I − II C. I − III D. III − II
- Materiał graficzny
Zadanie 1d
Describe two observations, other than the formation of gas bubbles, that would show that the reaction of sodium with water is exothermic.
Zadanie 8f
Ethane reacts with iodine vapour. C2H6(g) + I2(g) → C2H5I(g) + HI(g) (i) Calculate the enthalpy change of the reaction, ΔH, using section 12 of the data booklet. (ii) Draw and label an enthalpy level diagram for this reaction on the axes below.
- Materiał graficzny